自己写个一个队列和单例模式

package com.bjsxt.base.conn009;

import java.util.LinkedList;
import java.util.concurrent.atomic.AtomicInteger;
/**
 * 模拟Queue
 * @author alienware
 *
 */
public class MyQueue {

    private final LinkedList<Object> list = new LinkedList<Object>();
    
    private final AtomicInteger count = new AtomicInteger(0);
    
    private final int maxSize;
    private final int minSize = 0;
    
    private final Object lock = new Object();
    
    public MyQueue (int maxSize){
        this.maxSize = maxSize;
    }

    public void put (Object obj) {
        synchronized(lock){
            while(count.get() == maxSize){
                try {
                    lock.wait();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            list.add(obj);
            count.getAndIncrement();
            System.out.println(" 元素 " + obj + " 被添加 ");
            lock.notify();
            
        }
    }
    
    public Object take(){
        Object temp = null;
        synchronized (lock) {
            while(count.get() == minSize){
                try {
                    lock.wait();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            count.getAndDecrement();
            temp = list.removeFirst();
            System.out.println(" 元素 " + temp + " 被消费 ");
            lock.notify();
        }
        return temp;
    }
    
    public int size(){
        return count.get();
    }
    
    
    public static void main(String[] args) throws Exception {
        
        final MyQueue m = new MyQueue(5);
        m.put("a");
        m.put("b");
        m.put("c");
        m.put("d");
        m.put("e");
        System.out.println("当前元素个数：" + m.size());
        Thread t1 = new Thread(new Runnable() {
            @Override
            public void run() {
                m.put("h");
                m.put("i");
            }
        }, "t1");
        
        Thread t2 = new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    Thread.sleep(1000);
                    Object t1 = m.take();
                    //System.out.println("被取走的元素为：" + t1);
                    Thread.sleep(1000);
                    Object t2 = m.take();
                    //System.out.println("被取走的元素为：" + t2);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }, "t2");

        t1.start();
        Thread.sleep(1000);
        t2.start();
        
    }
    
    
    
}

package com.bjsxt.base.conn011;

public class DubbleSingleton {

    private static DubbleSingleton ds;
    
    public static DubbleSingleton getDs(){
        if(ds == null){
            try {
                //模拟初始化对象的准备时间...
                Thread.sleep(3000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            synchronized (DubbleSingleton.class) {
                if(ds == null){
                    ds = new DubbleSingleton();
                }
            }
        }
        return ds;
    }
    
    public static void main(String[] args) {
        Thread t1 = new Thread(new Runnable() {
            @Override
            public void run() {
                System.out.println(DubbleSingleton.getDs().hashCode());
            }
        },"t1");
        Thread t2 = new Thread(new Runnable() {
            @Override
            public void run() {
                System.out.println(DubbleSingleton.getDs().hashCode());
            }
        },"t2");
        Thread t3 = new Thread(new Runnable() {
            @Override
            public void run() {
                System.out.println(DubbleSingleton.getDs().hashCode());
            }
        },"t3");
        
        t1.start();
        t2.start();
        t3.start();
    }
    
}




内部类模式

package com.bjsxt.base.conn011;

public class InnerSingleton {
    
    private static class Singletion {
        private static Singletion single = new Singletion();
    }
    
    public static Singletion getInstance(){
        return Singletion.single;
    }
    
}